How to render a scene faster in Cycles?
You can't just &quot;render faster&quot; for the most part, there are really no shortcuts or magical tricks. You can optimize your scene, tweak settings, and adjust parameters. While these can under certain situations make a significant difference, they will most often lead to marginal speedups compared to the total duration of the process. These can add up frame upon frame when rendering long animations, yielding more significant benefits though, but don't expect miracles.
Rendering is by definition slow. It takes time, a lot of time and resources, rendering animations even more so; so be prepared to wait.
As a wise man once said

match your expectations to your hardware, or match your hardware to your expectations.

Time is money, if your are serious about rendering, if work depends on it, if you are making money out of it, or you are interested enough in your hobby invest in better hardware, or if you can't front the cash or prefer not to own it, rent computing power (a render farm, web services etc.).
Rendering speed is mostly a sum of variables like the performance capabilities of the infrastructure (computer, farm, available devices, among others), available resources, desired level of quality and scene complexity. Faster renders always come at a cost of sacrificing either render quality, money, or complexity of the scene.
That being said, for Cycles (and path tracing in general), there are a few setups that are slightly faster to calculate, and additionally there are numerous ways you can optimize your scene so it generates less noise. With less noise you could require less samples to achieve the same level of quality, hence taking less time to calculate, which results in faster rendering.
Generally speaking Cycles likes big and easy to find light sources. Path tracing is sort of like target practice, smaller or harder to reach or hidden lamps produce noisier output that needs more samples and takes longer to render. Things to avoid:

Lights

Very small light sources (spots, point lights or area lights with
small size or radius property)
Lamps hidden behind objects, in crevices or contributing indirect light to a scene
Lights behind or inside glass objects or refractive surfaces


Geometry

Very highly subdivided meshes
Mesh with Subdiv modifiers with adequate subdivisions for the viewport but very high rendering subdivisions value
Hidden or secondary objects with unnecessarily high quality meshes (generally speaking keep subdivisions and mesh density to the absolute minimum required for the desired quality and proportional to the objects importance in the overall scene)
Very dense meshes resulting from sculpting, 3D scans or importing from other CAD software


Shaders and materials

Very complex shaders trees or materials
Unnecessarily large image textures sizes
Lots of glossy materials and reflections (which cause fireflies)
Abusing bump maps
Small objects with emission shaders or illumination



Try searching the internet for &quot;Reduce Cycles noise&quot; or &quot;Optimize Cycles render&quot; and you will find plenty of tips about it like the ones bellow as an example:

How to avoid noisy renders in Cycles?
How to reduce fireflies in Cycles?
Will increasing samples reduce fireflies?
Blender Manual about optimizing scenes and reducing noise
Blender Guru tips about reducing fireflies
Noise reduction techniques YouTube Tutorial
..and more...

Modern versions of Blender now have multiple built-in options for denoising renders, which can cause blurry images and splotches when used incorrectly, but if used properly can help reduce the needed amount of samples save some rendering time. See:

How to properly denoise renderings?
Type of Denoiser built into Blender
Which denoiser is better?